Method

• 1.
  Preheat oven to 180°C. Grease a 20cm x 30cm lamington pan and line with baking paper, leaving 2cm overhang on each side.
• 2.
  Place butter and 1/2 cup (110g) sugar in a stand mixer with the paddle attachment and beat to combine. Beat in the flour to combine then press mixture evenly into the base of the prepared pan. Prick all over with a fork, then bake for 20 minutes or until golden. Reduce oven to 160°C.
• 3.
  Meanwhile, for the custard, whisk egg yolks, sugar and cornflour in a heatproof bowl until smooth. Place milk and vanilla in a saucepan over medium heat and bring to just below the boil, then remove from heat. Pour hot milk mixture over the egg mixture, whisking slowly until combined. Return mixture to saucepan and place over medium heat. Cook, stirring constantly with a whisk, for 5-6 minutes until a thick custard. Remove from heat and cool for 5 minutes. Strain through a fine sieve, then pour over the base. Cool for 10 minutes.
• 4.
  Arrange rhubarb pieces on top in 2 even rows. Bake for 30 minutes or until custard has set with a gentle wobble in the centre. While slice is baking, combine extra chopped rhubarb, remaining 1/4 cup (55g) caster sugar and 1/4 (60ml) cup water in a small saucepan over medium heat. Bring to a simmer and simmer rapidly for 4-5 minutes to break down rhubarb. Strain through a fine sieve. Remove slice from oven and brush over rhubarb syrup. Cool slice completely then chill before serving.